Bioethanol means ethanol derived from biological sources and is mainly produced by fermentation of carbohydrates contained in juice and the like from sugarcane and beet or of saccharified products of starch contained in corn, sweet potato, and the like (see Patent Document 1). For example, in the method according to Patent Document 1, saccharides (carbohydrates) are fermented to prepare acetic acid that is esterified and hydrogenated to produce ethanol.
In the production method of ethanol according to Patent Document 1, the fermentation process includes two steps of lactic acid fermentation and acetic acid fermentation. Furthermore, the acetic acid fermentation employs Clostridium bacteria, specifically, acetogenic bacteria such as Clostridium thermoaceticum and Clostridium formicoaceticum. 
There has been also developed a method for producing ethanol using biomass resources as a material (see Patent Document 2). In the method according to Patent Document 2, acidic hydrolysis or enzymatic hydrolysis of cellulose that is contained in biomass resources produces fermentative carbohydrates. Furthermore, the inventors of the present invention have developed a method in which lignocellulose is treated with pressurized hot water to prepare a wide variety of saccharides, the saccharides are converted into acetic acid by acetic acid fermentation, and the acetic acid is esterified and hydrogenated to produce ethanol (see Patent Document 3).